how to generate a flat file

hello every one
i want to export or create a fixed lenght flat file  from sql database my requirements are 
The export needs to be fixed length file that means each field will have predefined location and length like below: Field A: 20 char Field B: 15 char Field C: 10 char For following values see the flat file below: Field A                  Field B                  Field C Test 1                    Test 2                    Test 3 This is value 1    This is value 2    This is va ...